FIG. 1 illustrates a block diagram of a parallel transceiver module 2 currently used in optical communications, which has multiple transmit and receive channels. The transceiver module 2 includes a transmitter portion 3 a receiver portion 4. The transmitter and receiver portions 3 and 4 are controlled by a transceiver controller 6. The transmitter portion 3 comprises components for transmitting data in the form of amplitude modulated optical signals over multiple fibers (not shown). The transmitter portion includes a laser driver 11 and a plurality of laser diodes 12. The laser driver 11 outputs electrical signals to the laser diodes 12 to modulate them. When the laser diodes 12 are modulated, they output optical signals that have power levels corresponding to logic 1s and logic 0s. An optics system (not shown) of the transceiver module 2 focuses the optical signals produced by the laser diodes 12 into the ends of respective transmit optical fibers (not shown) held within a connector (not shown) that mates with the transceiver module.
Typically, a plurality of monitor photodiodes 14 monitor the output power levels of the respective laser diodes 12 and produce respective electrical feedback signals that are fed back to the transceiver controller 6, which processes them to obtain respective average output power levels for the respective laser diodes 12. The controller 6 outputs controls signals to the laser driver 11 that cause it to adjust the bias current signals output to the respective laser diodes 12 such that the average output power levels of the laser diodes are maintained at relatively constant levels.
The receiver portion 4 includes a plurality of receive photodiodes 21 that receive incoming optical signals output from the ends of respective receive optical fibers (not shown) held in the connector. The optics system (not shown) of the transceiver module 2 focuses the light output from the ends of the receive optical fibers onto the respective receive photodiodes 21. The receive photodiodes 21 convert the incoming optical signals into electrical analog signals. The transceiver controller 6 and/or other circuitry (not shown) of the transceiver module 2 processes the electrical signals to recover the data represented by the signals.
There is an ever-increasing demand in the optical communications industry for transceiver systems that are capable of simultaneously transmitting and receiving larger amounts of information. To accomplish this, it is known to combine multiple parallel transceiver modules of the type described above with reference to FIG. 1 to produce transceiver systems that have increased bandwidth. A variety of parallel transceiver modules are used in the optical communications industry for this purpose. For example, one known transceiver module of the type described above with reference to FIG. 1 includes a multi-fiber connector module known in the industry as the MTP® connector. The MTP connector module plugs into a receptacle of the transceiver module. The MTP connector module receives a duplex fiber ribbon (transmit and receive optical fibers) having a total of 4, 8, 12 or 24 optical fibers. When the MTP connector module is plugged into the receptacle, electrical contacts of the connector module are electrically connected with electrical contacts of a printed circuit board (PCB) of the transceiver module. The laser diodes and the photodiodes are integrated circuits (ICs) that are mounted on the PCB.
It is known that multiple transceiver modules of the type that use the MTP connector can be arranged in an array to provide a transceiver system that has an overall bandwidth that is generally equal to the sum of the bandwidths of the individual transceiver modules. One of the problems associated with such an array is that the MTP connectors are edge-mounted and the transceiver modules are stacked in racks. Although this type of array is a suitable solution in some scenarios for obtaining a transceiver system that has an increased bandwidth, there are limitations on the ability of such an array to achieve very large increases in bandwidth. For example, in order to obtain a transceiver system having the ability to simultaneously transmit and receive one terabit of data per second (Tb/s), the racks and cabling needed to accommodate the transceiver modules would consume so much space that the solution would be impractical in most cases. In addition, an array of this type would present heat dissipation problems, and in most cases would be prohibitively expensive.
Another parallel transceiver module that has multiple transmit and multiple receive channels is known in the optical transceiver industry as the Snap 12 transceiver module. The Snap 12 transceiver module comprises a 12-channel transmit module and a 12-channel receive module. The transmit and receive modules are mechanically coupled and electrically connected to a host PCB. Typically, the transmit and receive modules are mounted side by side on the host PCB. Each module has an array of 100 input/output (I/O) pins that plugs into a 100-pin ball grid array (BGA) of the host PCB. This type of BGA connection is commonly referred to as a mid-plane mounting connection due to the fact that I/O pins of the modules and the I/O pads of the BGA interconnect in the plane of the host PCB, or in a plane that is generally parallel to the plane of the host PCB. Thus, a mid-plane mounting connection is different from the edge-mounting connection described above with reference to the MTP connector.
The Snap 12 transceiver system has a bandwidth of 10 Gigabits (Gbs) per channel, and has a total bandwidth of 100 GB per second (Gb/s). The system is typically mounted in a box, which is connected to multiple electrical cables, which, in turn, are connected to multiple router ICs. In order to increase the total bandwidth of a Snap 12 system, multiple boxes may be used. Each of the boxes is connected to multiple cables, which, in turn, are connected to multiple router ICs. The boxes are mounted in racks. For example, to obtain a system having a total bandwidth of ½ Tb/s, a total of five Snap 12 boxes would be needed. The racks needed to accommodate this many boxes and the cables needed to interconnect the boxes to the router ICs consume a large amount of space and generate a large amount of heat. The space consumption and heat generation problems must be dealt with in order to make the system operate properly.
In addition, the Snap 12 transmit and receive modules are relatively tall (approximately 15 mm in height), which often results in the occurrence of relatively large impedance disturbances in the modules. These impedance disturbances reduce signal integrity, which limits the bandwidth efficiency of the system. In addition, each Snap 12 box is sold as a stand-alone part that is relatively expensive. Consequently, a system that is constructed of multiple boxes in order to achieve an increased bandwidth is generally very expensive.
A need exists for a transceiver system that has multiple parallel transceiver modules and that is capable of achieving large bandwidths of at least one Tb/s. A need also exists for such a transceiver system that is efficient in terms of space consumption, heat dissipation and costs. A further need exists for a transceiver system that is suitable for use as a router.